Tutorial One

Question 1

For each of the following binary relations R between X and Y, determine if it is one-to-one, one-to-many, many-to-one or many-to-many

1. X = students, Y = library books, (x,y) in R if student x has borrowed book y
2. X = students, Y = marks, (x,y) in R if student x got mark y in some unit
   
3. X = students, Y = marks, (x,y) in R if student x got mark y in CITS3240
4. X = students, Y = marks, (x,y) in R if student x got mark y in CITS3240 in 2006
5. X = students, Y = Australian mobile phone numbers, (x,y) in R if student x has mobile phone number y
6. X = students, Y = UWA student numbers, (x,y) in R if student x has student number y
   

Question 2

(Modified version of Exercise 2.2 from text)

In a university database, lecturers are identified by staff numbers and teach units identified by unit codes. Draw an ER diagram to reflect the following situations.

1. Lecturers can teach the same unit in several semesters and only the most recent offering is recorded.
2. Every lecturer must teach some unit.
3. Every lecturer teaches exactly one unit (no more, no less).
4. Every lecturer teaches exactly one unit, and each unit must be taught by some lecturer.
5. Some units can be taught by groups of lecturers jointly, but it is possible that no one lecturer can teach the unit alone. [Hint: you will need to introduce a new entity set and relationship set to model this.]
   

Question 3

(Modified version of Exercise 2.5 from text)

Notown Records is going to create a database to store information about its business. Draw an ER diagram to model their business activities based on the following requirements:

1. Each musician has a real name, a phone number and a unique stage name.
2. Each instrument used in Notown recordings has a name (guitar, synth etc) and a musical key (C, B-flat etc).
3. Each album recorded at Notown has a title, a copyright date, a format (CD, vinyl etc) and an album identifier.
4. Each song recorded at Notown has a title and an author.
5. Each musician may play several instruments, and each instrument may be played by several musicians.
6. Each album has a number of songs on it, but no song may appear on more than one album.
7. Each song is performed by one or more musicians and a musician may perform a number of songs.
8. Each album has exactly one musician acting as a producer, and a producer may produce several albums.

Make sure your ER diagram contains all the constraints that you can model, and indicate any constraints that you cannot model with this ER diagram.

Question 4

(Web research question)

What is a Turing-complete programming language? Is SQL Turing-complete? Is this a good thing or a bad thing?